MEMS Optical Microphone With Oversized Beam for Dynamic Range
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Solution Overview
Problem
Conventional microphones based on capacitors have limitations in dynamic range and sensitivity, failing to effectively capture a wide range of sound signals and linear changes in sound pressure.
Innovation Solution
An MEMS optical microphone design with a larger light beam than the maximum aperture size, incorporating a diffuser section and multiple independent membranes with distinct aperture sizes, and a symmetrical diaphragm configuration to enhance dynamic range and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitor-based microphone is used, then the structure is simple, but the dynamic range and sensitivity are limited
Solution Approach 1:
The patent replaces the conventional capacitor-based electrical sensing mechanism with an optical measurement system. A light source emits light through the diaphragm aperture to a photodetector, and changes in aperture size due to acoustic pressure are detected as changes in light intensity. This optical substitution enables higher sensitivity and wider dynamic range while maintaining a relatively simple MEMS structure.
Solution Approach 2:
The patent changes the measurement parameter from electrical capacitance to optical transmission. By measuring the intensity of light transmitted through the aperture rather than electrical properties, the system achieves improved sensitivity and dynamic range. The optical parameter provides a more linear response to aperture size changes, enhancing measurement precision.
2Productivity
If the light beam size is smaller than the aperture size, then the optical system is compact, but the dynamic range is limited
Solution Approach 1:
The patent deliberately makes the light beam size larger than the maximum aperture size, which appears excessive at first glance. This ensures that the light beam always fully covers the aperture throughout its entire range of motion, allowing the photodetector to accurately measure all aperture openings without saturation or clipping, thereby maximizing the dynamic range of sound signal detection.
Solution Approach 2:
The oversized light beam serves multiple functions: it ensures complete coverage of the aperture at all positions, provides a linear measurement range for the photodetector, and maintains measurement accuracy across the full dynamic range of acoustic pressures. This single design choice achieves universal coverage for all operating conditions.
3Measurement precision
If a single diaphragm is used, then the structure is simple, but the linear sensing range is limited
Solution Approach 1:
The patent divides the diaphragm into multiple independent membranes (typically two), each with its own aperture. This segmentation allows each membrane to be optimized for different portions of the acoustic pressure range, with each aperture sized to operate in its optimal linear range. The combined output of multiple segments extends the overall linear sensing range beyond what a single diaphragm could achieve.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design improves the dynamic range and sensitivity of the MEMS optical microphone, enabling wider sound signal detection and higher sensitivity to linear changes in sound pressure.
Implementation Method 1
The optoelectronic module converts the intensity and phase signal of the reflected light into an electrical signal
Implementation Method 2
the light beam includes a diffuser section, a size of the diffuser section gradually increases along an extending direction of the light beam
Data Source
AI summary
An MEMS optical microphone, including a casing including an inner cavity and a sound inlet that communicates the inner cavity with outside; an MEMS module including a diaphragm suspended in the inner cavity, an aperture is provided penetrating through the diaphragm, and a size of the aperture increases or decreases with acoustic pressure applied to the diaphragm; an optoelectronic module including an electromagnetic radiation source and a sensor arranged on opposite sides of the diaphragm, the sensor is configured to receive a light beam emitted by the electromagnetic radiation source, the light beam covers the aperture, and a size of the light beam is larger than a maximum size of the aperture; and an integrated circuit module electrically connected with the MEMS module and the optoelectronic module. Dynamic range of the MEMS optical microphone is improved, wider range of sound signals can be sensed, and higher sensitivity can be realized.